<!DOCTYPE html>
<title>CSS Anchor Positioning: Invalidation when the anchor*() fallback matches old style</title>
<link rel="help" href="https://drafts.csswg.org/css-anchor-position-1/">
<link rel="help" href="https://issues.chromium.org/issues/333858786">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
  #cb {
    position: relative;
    width: 200px;
    height: 200px;
    border: 1px solid black;
  }

  #anchor {
    anchor-name: --a;
    position: absolute;
    width: 40px;
    height: 30px;
    left: 75px;
    top: 75px;
    background: coral;
  }

  #anchored {
    position: absolute;
    background: seagreen;
    width: 50px;
    height: 50px;
  }

  #anchored.change {
    /* The fallbacks match what the unchanged style says, but we shouldn't
       take the fallbacks here. */
    width: anchor-size(--a width, 50px);
    height: anchor-size(--a height, 50px);
  }
</style>
<div id=cb>
  <div id=anchor></div>
  <div id=anchored>X</div>
</div>
<script>
  test(() => {
    assert_equals(anchored.offsetWidth, 50);
    assert_equals(anchored.offsetHeight, 50);

    anchored.classList.toggle('change');

    assert_equals(anchored.offsetWidth, 40);
    assert_equals(anchored.offsetHeight, 30);
  }, 'Correct invalidation when fallbacks match the old style');
</script>
